Electrosurgery is a widely used surgical procedure for treating tissue abnormalities. For example, it is known to use radio frequency (RF) energy to treat or ablate cancerous lesions in the liver, kidney, lungs and other soft tissues. RF ablation occurs as a result of a high frequency alternating current (AC) flowing from the tip of an electrode through the surrounding tissue. Ionic agitation is produced in the tissue around the electrode tip as the ions attempt to follow the change in direction of the alternating current. This ionic agitation creates frictional heating and necrosis of the tissue around the electrode. Such procedures may be performed through an open abdominal incision or via laparoscopy which is performed through multiple, small skin incisions, and can also be conducted percutaneously through small skin incisions.
Electrosurgical devices that can be used for tissue ablation using RF energy generally fall into one of two categories, monopolar devices and bipolar devices. Monopolar electrosurgical devices typically include an electrosurgical probe having a first or “active” electrode extending from one end. The electrosurgical probe is electrically coupled to an electrosurgical generator, which provides a high frequency electrical current. During an operation, a second or “return” electrode, having a much larger surface area than the active electrode, is positioned in contact with the skin of the patient. The surgeon may then bring the active electrode in close proximity to the tissue and activate a switch, which causes electrical current to arc from the distal portion of the active electrode and flow through tissue to the larger return electrode. Bipolar electrosurgical devices do not use a return electrode. Instead, a second electrode is closely positioned adjacent to the first electrode, with both electrodes being attached to an electrosurgical probe. As with monopolar devices, the electrosurgical probe is electrically coupled to an electrosurgical generator. When the generator is activated, electrical current arcs from the end of the first electrode to the end of the second electrode and flows through the intervening tissue. The gauge or size of electrodes of RF ablation probes is often minimized in order to reduce trauma to the surgical site and facilitate accurate placement of the probe so that target tissue can be ablated with minimal damage to surrounding healthy tissue.
One known bipolar electrosurgical probe configuration is shown in FIGS. 1-3. A typical bipolar electrosurgical probe 10 includes electrode or needle members 12 and 14 and an insulation member 16 between ends of the electrodes 12 and 14 to provide bipolar modality. In known devices, the insulation member 16 is a non-conductive glue or adhesive. A distal end 13 of one electrode 12 and a proximal end 15 of another electrode 14 are attached to the insulation member there between. Glue may flow over the edges of the electrodes 12 and 14 and be smoothed or flush with the electrodes if the electrodes are machined with a lathe.
While such electrosurgical probes have been used effectively in the past, they can be improved. In particular, the strength and durability of bipolar electrosurgical probes can be enhanced to withstand forces and loads that are encountered during placement and removal of the probes. For example, the insulation glue or plastic member 16 positioned between ends of two conductive electrodes 12 and 14 is flexible relative to the electrodes 12 and 14, which are typically stainless steel. The flexible glue or plastic insulation member 16, therefore, is a weak point in the probe.
For example, referring to FIG. 4, during use, the tip 18 of the probe 10 may encounter bone or another hard material 20. The stainless steel electrodes 12 and 14 can withstand these forces, but the probe 10 may buckle or kink 30 at the weak point of the probe 10, i.e., at the glue or plastic insulation member 16. These types of failures may be more common when using probes having small diameter or thin walled electrodes 12 and 14, which are used to reduce trauma to surrounding tissue. Thus, while smaller and thinner electrodes reduce tissue trauma, they also have weaker insulation members 16 and are more likely to buckle or kink. Thus, the desire for small electrode dimensions to reduce tissue trauma must be balanced against a probe having sufficient strength to withstand compression, tension and torque or rotational forces or loads encountered during ablation procedures.
Accordingly, it would be desirable to have electrosurgical probes with improved strength and structural integrity. Further, it would be desirable to have such improved strength and integrity while maintaining small electrode dimensions to reduce trauma to surrounding healthy tissue.